Coated board, a process for its manufacture, and containers and packaging formed therefrom

ABSTRACT

The invention relates to coated board, a process for its manufacture, and containers and packaging formed therefrom. The board comprises at least one polymer-based coat preventing the transmission of liquids and gases, which coat is according to the invention made from a polymer dispersion to which talc particles are added so that talc will constitute 30-80% of the dry weight of the dried coat. The coating is applied onto the board during its manufacture as on-line coating. The board may be, for example, a multi-layer board ( 2 ) which has a middle layer ( 6 ) containing CTMP or other similar mechanical pulp, on its both sides outer layers ( 7 ) formed from sulfate pulp, against these on both sides of the board ( 2 ) talc-containing polymeric barrier layers ( 3 ), and on one side of the board a heat sealing layer ( 9 ) introduced onto the barrier layer ( 3 ).

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/FI98/00442 which has an internationalfiling date of May 27, 1998, which designated the United States ofAmerica.

FIELD OF THE INVENTION

The present invention relates to coated board comprising at least onepolymer-based coat which prevents the penetration of liquids and gases.Furthermore, the invention comprises a process for manufacturing theboard, and dishes and packaging, such as food packaging formed from theboard

DISCUSSION OF RELATED ART

The board used for packaging liquid foods and other products sensitiveto spoiling must, for the sake of the durability of the product, beimpermeable to liquid and gas. Such packaging board prevents airborneoxygen from penetrating to the inside of the package and, consequently,the product from spoiling and, respectively, the aromas which evaporatefrom the product from escaping from the package. In board used fordisposable containers, it is important to have a liquid-resistant coatwhich protects the board from wetting.

One known method for rendering product packaging impermeable to liquidand gas is to provide the board used for the packaging with a metalfoil. However, the disadvantages of such packaging include highmanufacturing costs, non-biodegradability of the foil layer, problems ofregeneration of the packaging material, and the unsuitability of thepackaging for heating in a microwave oven.

Because of the said problems associated with metal foil, a shift hasbeen made in food packaging to increased use of boards in which theimpermeability to liquid and gas has been achieved by means of one ormore polymeric barrier layers. Among polymer materials, especially EVOHhas excellent barrier properties but, for example, polyamide is alsousable for the purpose. By combining various polymer materials, animpermeability substantially corresponding to that of aluminum foil hasbeen achieved, but owing to the required successive barrier and bondingagent layers the board becomes complicated in structure and theconsumption of polymer material is high.

The special problems of EVOH in packaging boards include its mechanicalweakness and sensitivity to moisture. During the heat sealing of theboard, the EVOH layer tends to be perforated by the steam escaping outof the board. In these respects polyamide is a material more durablethan EVOH ,but its barrier properties are not equal to those of EVOH.There are known packaging boards in which the solution to the problemhas been sought through a suitable combining of EVOH and polyamide. Acommon problem associated with on-line coating of boards with polymerscontinues to be the risk of sticking during the rolling subsequent tothe drying of the coat. The sticking will damage the coat, which shouldspecifically be unbroken and continuous in order to provide the desiredimpermeability to oxygen and water vapors. The large amount of polymericmaterial present in the coating layers also detract from the pulpabilityof the board during its recycling.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a board provided witha polymer-based coat impermeable to liquids and gases, substantiallyavoiding the said disadvantages associated with known coated boards.Board according to the invention is characterized in that the coat isformed on the board during its manufacture from a polymer dispersionapplied as on-line coating, to which dispersion talc particles have beenadded so that the talc will constitute. 30-80% of the total weight ofthe dried coat.

In the coated board according to the invention, impermeability to water,water vapor, oxygen and aromas can be achieved by means of suitablebatching of talc, in addition to which the coat is impermeable to fatsand oils. The barrier properties of the coat are based on the presenceof a very pure talc made up substantially of small, flaky particles,typically less than 50 μm in size, while the polymer closing the gapsbetween the talc particles forms a continuous phase which finallyensures the impermeability of the coat. It should be noted that callingthe coat polymer-based refers to the presence of the. said continuouspolymer phase and not to the polymer necessarily constituting thelargest ingredient proportion in the coat, a fact which can be observedeven from the range of the weight proportion of talc.

Besides the achievable barrier properties, the talc-containing coat ofboard also has many other advantages over known coating materials. Thetalc-containing coat is not sensitive to moisture; it protects the boardfrom wetting so that the board retains its mechanical strength. Thecoating is thus especially suitable. for disposable containers and forpackaging of liquid foodstuffs. The talc-containing coating compound isalso suitable, without problems, for on-line coating processes which arein use, and the coating does not have a tendency to stick when thecompleted board is wound on a roll. The coating withstands heating, forwhich reason the coated board is suitable, for example, for bakingcontainers. The coating also improves the mechanical properties of theboard by increasing its stiffness.

Furthermore, the talc-containing coating has good printing propertiesowing to the fact that its surface is not hydrophobic. It is possible tocarry out printing without a corona treatment, which is required by manyother polymers, such as polyethylene, used as coatings.

Since the presence of talc in the coating compound reduces the amount ofpolymeric coating material, the coated board according to the inventionis better pulpable and thus easier to recycle than known boards havingcorresponding barrier properties. For the same reason the use of talc ispreferable in terms of the compostability and biodegrability of theboard.

DETAILED DESCRIPTION OF INVENTION

A talc-containing coat is in itself transparent, which maybe anadvantage in some uses of the board. On the other hand, thetalc-containing coating compound can be easily colored by addingpigments to the polymer dispersion forming the coat, applied onto theboard.

The oxygen and water vapor barrier properties of a talc-containing coatdepend on the basis weight of the coat and the amount of talc therein.Generally speaking, the dry weight of an individual talc-containing coaton either side of the board may vary within a range of 2-40 g/m².Preferably the weight of the coat is 5-40 g/m², by means of which it ispossible to achieve impermeability of the coat to water vapor, and mostpreferably within a range of 8-20 g/m², in which case the coat can bemade impermeable to oxygen, a so-called High Barrier coating with anoxygen permeability below 100 cm³O₂/m²·d. The proportion of talc is30-80%, preferably 40-75%, of the weight of the dried coat.

Polymers suitable for the polymer basis of a coat according to theinvention for a board include styrene butadiene, styrene acrylate,acrylate or vinyl acetate polymers and copolymers, or blends of these.The polymer may be prepared by using a monomer blend containing as itsprincipal components vinyl acetate and a (methyl, ethyl, propyl orbutyl) ester of acrylic acid and/or methacrylic acid and/or loweralcohols, or by using a monomer blend containing as its principalcomponents styrene and a (methyl, ethyl, propyl or butyl) ester ofacrylic acid and/or methacrylic acid and/or lower alcohols or by using amonomer blend containing as its principal components a (methyl, ethyl,propyl or butyl) ester of acrylic acid and/or methacrylic acid and/orlower alcohols and/or a copolymer of these. The said polymers formpolymer latexes, i.e. polymer dispersions, which can be combined withtalc particles and be applied onto board as a coat in which dispersedpolymer particles join one another as a polymer phase which binds thetalc particles together. Furthermore, polylactides,polyhydroxybutyrates/polyhydroxy-valerates, modified starches and otherbiopolymers which are compostable or entirely biodegradable can bementioned as usable polymers which are especially advantageous.

The colorability, already pointed out above, of a talc-containing coatis an especially advantageous property, in particular in the packagingof foods which must be protected from the detrimental effect ofultraviolet light. The coat of board intended for food packaging maythus advantageously contain, in addition to talc, also some coloringpigment in an amount of at maximum 5% of the total coating layer. Forexample, soot, metal pigments, mineral pigments and organic pigments canbe used.

In addition to talc, the coat may contain some other mineral componentwhich serves as a filler. Examples of such components, the weightproportion of which is most preferably at maximum 30%, include titaniumdioxide, calcium carbonate, kaolin and gypsum.

In a board to be used for food packaging and containers it may bepreferable to incorporate into the coating compound a hydrophobic agent,for example, a wax dispersion such as paraffin wax, PE wax or a AKD waxdispersion, in an amount of at maximum 20% of the total weight of thecoat. A hydrophobic coat, decreases the tendency of the food to adhereto the board. Wax, and a mineral pigment used together with it,additionally reduce the sticking together of the dried coats duringrolling. A high wax content may, on the other hand, weaken the printingproperties of the surface.

The forming of a coat on a board is preferably carried out by applying atalc-containing dispersion onto the board in two or more successivesteps, the dispersion applied in the preceding step being dried beforethe subsequent application step. By such a step-wise coating procedure acoat of a better quality is achieved than by applying the entire amountof dispersion for the coat onto the board at one time.

Board intended for heat sealable packaging can, in addition to atalc-containing coat according to the invention, be provided with one ormore polymeric heat sealing layers adhering to the coat. There may thusbe a talc-containing coat on one side of the board and a heat sealinglayer sealable to the said coat on the opposite side of the board.Alternatively, both sides of the board may be provided with a heatsealing layer, in which case at least on one side of the board the heatsealing layer is applied on top of a talc-containing coat. Suitablematerials for the heat sealing layer include LD-polyethylene and heatsealing lacquers.

Since the heat sealing layer, contrary to the talc-containing coat, mayin order to be printable require a corona treatment, it may beadvantageous to introduce the heat sealing polymer onto the board onlyin narrow streaks in the areas of the heat seals to be produced. Thusthe said polymer will not complicate the printing of the areas betweenthe seals. At the same time, savings of material are achieved and thestructure of the board and the products made therefrom is renderedlighter.

A board according to the invention, provided with a talc-containingpolymer coat, is most preferably a multi-layer board comprising two ormore fiber-based layers; its weight without the coats may be within arange of 130-500 g/m², preferably 170-350 g/m². One example is athree-layer board which comprises a thicker middle layer which is formedin part or entirely from a mechanical pulp, such as CTMP; on both sidesof the middle layer there are thinner outer layers formed from a sulfatepulp. Onto the outer layers on both sides of the board there areintroduced polymeric coats which, in accordance with the invention,include at least one talc-containing barrier layer. The said board initself has a stiff and non-buckling structure, and the talc-containingcoat according to the invention on one or both sides of the board givesthe board additional stiffness. The talc-containing barrier provides thefurther advantage that the ingredients of wood origin present in. themechanical pulp will not give detrimental odor or taste to the packagedproduct. If recycled paper pulp is used for making the board, thebarrier layers correspondingly insulate the product from any impuritiespresent in the board.

The process according to the invention for the manufacture of the coatedboard described above is characterized in that, in connection with themanufacturing process, there is applied onto the board as on-linecoating a polymer dispersion to which talc particles are added so thatin the completed board talc will constitute 30-80% of the total weightof the dried coat.

Of packaging according to the present invention, made from board inaccordance with the above, there must be mentioned, above all, foodpackaging in which the talc-containing barrier layers of the boardensure the durability of the product. Products packaged in accordancewith the invention are protected from airborne oxygen and from outsidemoisture, while the water, fat and aroma barrier properties of the coatpreserve the quality of the product and prevent packaged products fromdamaging one another during storage. Examples of products to be packagedinclude moist or liquid foods, such as juices, water, milk and othermilk products such as cream, buttermilk, yogurt and ice-cream. Alsopossible are dry foods such as flours, powders, breakfast cereals, andanimal foods. For example, the inside plastic bags so far used inbreakfast cereal packages will be unnecessary.

The board can be used not only for industrial product packaging but alsofor manufacturing various containers, such as disposable tableware. Theshape of the package or container is not limited; cases, cartons, tubs,baking containers, cups, mugs, goblets, trays, plates, etc., arepossible.

An especially advantageous area of application for products according tothe invention consists of board for frozen-foods containers, in which aninside talc-containing coat prevents the product from sticking to thecontainer. Examples of frozen products to be packaged include ready-madefoods such as casseroles and ice-cream.

The packaging of products, other than foods requiring shielding againstthe transmission of oxygen, moisture and aromas may also come within thescope of the invention. One example is cigarette boxes in which thetalc-containing coat of the packaging board renders unnecessary. thealuminum foil shield used inside the boxes to date.

Uses outside the packaging field for coated board according to theinvention further include post-cards and advertising posters. In thelatter, coats which protect the board layer from wetting are aconsiderable advantage.

BRIEF DESCRIPTION OF DRAWINGS

The invention is described below in greater detail with the help ofexamples, initially with reference to the accompanying drawings, wherein

FIG. 1 depicts a frozen-foods container formed from board according tothe invention,

FIG. 2 depicts a cross-section of the edge of the container in anenlargement of FIG. 1,

FIG. 3 depicts schematically the layered structure of the board used inthe container according to FIGS. 1 and 2,

FIG. 4 depicts schematically a layer-structured board according toanother embodiment of the invention,

FIG. 5 depicts a disposable mug formed from a board according to theinvention,

FIG. 6 depicts the layered structure of the board used in the mugaccording to FIG. 5, and

FIG. 7 depicts the structure of one further board according to theinvention.

DETAILED DESCRIPTION OF INVENTION

The frozen-foods container 1 according to the invention, shown in FIGS.1 and 2, suitable for example for packaging processed foods, is made ofboard 2 which is on the inside of the container coated with apolymer-based coat 3 which contains dispersed talc particles. The coat 3serves as an oxygen and aroma barrier for the product in the closedcontainer and at the same time protects the board 1 from moisturederived from the product.

The structure of the coated board used for the frozen-foods container 1according to FIGS. 1 and 2 is shown in greater detail in FIG. 3. Thecoat 3 is made up of a primer coat 4 of a talc-containing polymerdispersion, applied onto the board 2, and a top coat 5 of the samedispersion, on top thereof. These coats serve as a water, fat and oxygenbarrier protecting the board 2. According to the example, the weight ofeach coat 4, 5 is 10 g/m². The three-layer board 2 under the coat isaccording to FIG. 3 made up of a thicker middle layer 6 which is a blendof sulfate pulp and CTMP and of thinner outer layers 7 on both sides ofthe middle layer, the outer layers being of sulfate pulp. The proportionof the middle layer 6 is approx. 60% and that of each outer layer 7approx. 20% of the weight of the board 2. The total weight of the board2, without the coats, is, for example, approx. 225 g/m².

FIG. 4 shows a coated board according to the invention which differsfrom that shown in FIG. 3 only in that the board 2 is provided on eachside with a polymer-based coat 3 which contains talc particles, servingas a barrier. Each coat 3 is formed by a two-step coating process inwhich first a primer coat 4 is formed and thereafter a top coat 5.

FIG. 5 depicts a disposable drinking mug 8 according to the invention,and FIG. 6 shows the layer-structured board used for making it. Thisembodiment of the board differs from that shown in FIG. 4 in that on oneside of the board there is topmost a heat sealing layer 9 of LDPE. Theheat sealing layer 9 is applied onto the talc-containing coat 3 withouta bonding agent layer between them. The talc-containing coats 3 may bemade up of primer and top coats 4, 5 in a manner corresponding to FIGS.3 and 4. In the mug 8 the board is oriented so that the inner surface 10of the mug is formed by the LDPE layer 9 and the outer surface 11 isformed by the talc-containing coat 3 which constitutes a barrier. At theseal 12 the layers 3, 9 of the opposite sides of the board are heatsealed to each other.

The layer-structured board according to FIG. 7 differs from that shownin FIG. 6 in that the heat sealing polymer is applied onto one side ofthe board only as a streak 14 at the heat sealing point. Outside theheat sealing points 14 the board surface is made up of a talc-containingbarrier 3. This option saves heat sealing polymer and improves theprintability of the surface.

Instead of LDPE it is possible to use for heat sealing a lacquer whichis applied onto the packaging blanks in connection with the printing inthe printing press.

The invention is illustrated further with the following embodimentexamples.

EXAMPLE 1

Talc, either as a powder or granulated, was slurried in water accordingto the following formulation: 1585.6 g of water, 4.1 g of sodiumpolyacrylate and 16.2 g of sodium carboxymethyl cellulose were weighedinto a dispersion vessel. High rotation speeds were used in thedispersion in order to break up talc agglomerates. Talc was added to themixture gradually, in total 2700.0 g. Halfway through the adding of thetalc, a further 4.1 g of sodium polyacrylate and 2.4 g of sodiumhydroxide were added. The dispersing vessel was equipped with a coolingmantle, and the cooling of the slurry was started at 20 min from theending of the talc adding step. Thereafter the dispersing was continuedfor another 20 min. The product obtained was a talc slurry having asolids content of 63.0% and a viscosity of 200 mPas, measured by using aBrookfield LVT viscometer with measuring head No. 3, at a rotation speedof 100 r/min. The final coating compound was obtained by mixing the talcslurry with a polymer latex.

EXAMPLE 2

Talc, either as a powder or granulated, was slurried in a polymer latex,according to the following formulation: 181.1 g of water, 1700.0 g of apolymer latex based on styrene butadiene (solids content 50%, secondorder transition temperature +20° C.), 3.4 g of sodium hydroxide and 1.7g of organomodified siloxane were weighed into a dispersion vessel. Highrotation speeds were used in the dispersing in order to break up anytalc agglomerates. Talc was added to the mixture gradually, in total1700.0 g. The dispersion vessel was equipped with a cooling mantle, andthe cooling of the slurry was started at 20 min from the ending of thetalc adding step. Thereafter the dispersing was continued for another 20min. The product obtained was a coating compound having a solids contentof 68.0% and a viscosity of 1150 mPas measured by using a Brookfield LVTviscometer with measuring head No. 4, at a rotation speed of 100 r/min.

The following examples describe the effect of completed coatingcompounds prepared by the technique according to Examples 1 and 2,applied onto board, on the properties of the board. The permeabilitymeasurements in the examples were made, unless otherwise stated, in thefollowing conditions:. air temperature 23° C. and relative humidity 50%.The unit for water permeability was g/m², for water vapor permeabilityg/m²·d, and for oxygen permeability cm³/m²·d.

EXAMPLE 3

A styrene-butadiene-based coating compound which contained differentamounts of talc was applied by means of a laboratory coating machineonto a board, from which water vapor transmission rates (WVTR) weremeasured. The transmission rates of the coatings are shown in Table 1.

TABLE 1 Proportion of talc in coating compound (%) 9 20 35 50 65 80Coating thickness (μ) 10 9.5 10 10 7.5 7.5 WVTR (g/m2 · d) 15 10.8 9.8 97 6.2

EXAMPLE 4

Value PA in Table 2 shows the pulpability properties of board treatedwith a coating compound which contained a talc-containing polymer latexbased on styrene butadiene. The value was determined as follows: thetreated board was disintegrated according to the method SCAN-C 18:65.Laboratory sheets were prepared from the stock. The quality of the sheetwas assessed on a scale of 0-5, where 0 stands for good pulpability (noaccumulations due to the coating compound are observed) and 5 stands forpoor quality (a great deal of accumulations of the coating compound orunevenness due to poor disintegration of the pulp).

TABLE 2 Proportion of talc in coating compound 0 20 40 60 80 PA 4 3 2 10

EXAMPLE 5

This example illustrates differences in the permeability properties ofthe coating, when the same coating compound, which contains a polymerlatex based on styrene butadiene and has a talc content of approx. 50%,is applied onto board either once or twice so that the final thicknessof the dry coat in each case is the same, approx. 14 μm. Table 3 showsthe effect of the two different application concepts on both the watertransmission and the water vapor transmission of the coat.

TABLE 3 Number of coatings 1 coating 2 coatings Cobb600 (g/m2) 1.2 0.6WVTR (g/m2 · d) 9.8 7.5

EXAMPLE 6

Onto a 285 g/m² board there was first applied a coating compound with acomposition of a talc-containing polymer latex based on styrenebutadiene 50% and a polymer latex based on polyvinyl acetate/acrylate50%. On top of the first coat there was applied a second coat whichcontained a talc-containing polymer latex based on styrene butadiene,calcium carbonate and wax. The amounts of coating compound in both coatswere approx. 10 g/m² solids. Table 4 shows the water transmission andwater vapor transmission properties given to the coat by the combinationof the said coating compounds.

TABLE 4 Cobb600 (g/m2) 0.6 WVTR (g/m2 · d) 2.8

EXAMPLE 7

Onto a 285 g/m² board there was applied a coating compound having acomposition of talc 50% and, in varying proportions. a polymer latexbased on styrene butadiene and a polymer latex (second order transitiontemperature +60° C.) based on butyl acrylate The amount of coatingcompound was approx. 12 g/m² solids. Table 5 shows the waterpermeability properties given to the coat by the said combination ofcoating compounds.

TABLE 5 Proportion of styrene butadiene in the polymer latex, % 0 10 2040 60 80 90 100 Cobb600 (g/m2) 2.1 1.5 2.6 2.7 5.0 10.3 20.1 32.6

EXAMPLE 8

A coating compound which contained talc approx. 65% and a polymerapprox. 35% was used for coating board at a speed of 450 m/min in aboard machine. The coating was carried but both as a single coating andas a double coating. The transmissions of water, water vapor, fat, andoxygen were measured from the samples obtained. The fat resistance testwas carried out according to the ASTM standard. The results obtained arecompiled in Table 6.

TABLE 6 Amount of coating compound (g/m2) Cobb 900 WVTR O2TR Oilresistance 8 30 41 no transmission 15 8 11 50-100 no transmission

EXAMPLE 9

A coating compound which contained talc approx. 65% and a polymerapprox. 35% was used for pilot coatings from which transmission rateswere measured. Board was coated both on one side and on both sides. Theresults are in Table 7. The water vapor measurement conditions were:temperature 28° C. and relative humidity RH 50%.

TABLE 7 Amounts of coating (g/ Fat m2) on top Cobb resist- Board gradeside/back side 600 WVTR Pinholes ance Drinking cup 0/26 <1 7.5 none >1 dboard CTMP-containing 0/20 2 16.5 none >1 d board Other solid 9/36 <1 11none >1 d board

EXAMPLE 10

The pulpability and stickiness of a dispersion coating compound whichcontained talc approx. 65% and a polymer approx. 35% were studied in apilot paper machine pulper and with wet end recycling. The amounts ofcoating were within a range of 20-40 g/m², and the boards used wereboards according to Example 9. The pulping temperature was 40-60° C. andthe pulping time was 1-3 hours. The pulp thus obtained was run throughthe pilot paper machine for a total of 15 hours during three days whileminimizing the water consumption of the paper machine. According to theresults the pulping was very successful and no sticky substancesaccumulated on the wire during the entire time. The analysis of the tailwater yielded results corresponding to normal waste pulp.

EXAMPLE 11

A coating compound containing talc approx. 12 g/m², the proportion oftalc being approx. 35% and the proportion of polymer approx. 65%, wasapplied onto the surface of board by means of a pilot coating machine.This coat was heat sealed against itself; against a fiber material andagainst PE. Table 8 shows the sealing results, 0 standing for a poorseal and 5 a perfect seal.

TABLE 8 Sealing temperature ° C. 80 100 120 140 160 180 Coating-coating0 5 Coating-fiber 2 4 5 Coating-PE 0 1 5

EXAMPLE 12

A coating which contained talc approx. 65% and a polymer approx. 35% wasused for coating a three-layer board (Enso Natura L 240 g/m²) both onone side and both sides of the board. In the middle layer of the board,CTMP was used in addition to chemical pulp. The reference samples werean uncoated board and boards pigment-coated on one side and on bothsides. The estimated amount of coating compound in each coat was approx.10 g/m².

The board was subjected to a Cobb test (5 min) , whereafter thestiffness was measured from the samples wetted in the Cobb test.According to the results, the stiffness of a board coated with a coatingcompound of the type of Example 2 was approx. 90%; of the originalstiffness, whereas the stiffness of the pigment-coated board and theuncoated board was only 25% of the original stiffness.

The results of the measurements are shown in Table 9.

TABLE 9 Cobb 5 min Bending resistance (mN) (g/m2) before after Board 40211 75 Board + pigment 54.5 227 60 Board + pigment on both sides 57.6250 61 Board + coating of Example 2 3.3 212 181 Board + coating ofExample 2 2.5 224 214 on both sides

EXAMPLE 13

35 g of oxidized starch Raisamyl 302P was slurried in 150 g of water andwas transferred to a pressure-resistant reactor vessel. The temperatureof the mixture was raised to 100° C. and was kept at that for 20 min todissolve the starch grains. Thereafter the mixture was cooled to 70° C.,and a solution which contained 2.5 g of sodium lauryl sulfate in 50 mlof water was added to it. To this mixture there was added gradually inthe course of two hours from a pressure burette a monomer blend whichcontained 117 g of styrene and 74 g of a butadiene washed with a lyesolution,. as well as 3 g of acrylic acid. From another pressureburette, an initiator solution was added which contained 3 g of ammoniumpersulfate in 70 g of water. The polymer reaction was allowed tocontinue for 12 hours. The product obtained was a white dispersionhaving a solids content of 46% and a viscosity of approx. 900 mPas,measured by using a Brookfield LVT viscometer with measuring head No. 2,at a rotation speed of 100 r/min. The measurements were carried outafter the product had been neutralized with NaOH to a pH of 7. Thecalculated starch content of the product was approx. 13%.

95.2 g of a talc slurry according to Example 1 was mixed with 304.3 g ofa polymer dispersion according to the above method. The talc slurry wasadded to the polymer dispersion gradually for 10 min by using relativelyhigh rotation speeds. 4 g of an organomodified polysiloxane was added tothe 399.5 g of coating compound obtained. The solids content of thefinal coating compound was approx. 50%. The obtainedpolymer-dispersion-based coating compound was applied by means of alaboratory coating machine once onto a 265 g/m² board and was dried byusing an IR drier to a final moisture content of 6%. The dry weight ofthe coat was approx. 12 g/m². The water vapor transmission rate (WVTR)was measured from the dispersion-coated board at a temperature of 23° C.and a relative air humidity of 50%. The water vapor transmission rateobtained by a gravimetric method was approx. 32 g/m², 24 h.

What is claimed is:
 1. A frozen food container made of a coated board,the container having the shape of a cup or tray, and the boardconsisting of a fiber board base of a weight from 130-500 g/m² and oneor more superimposed polymer-based coat layers, said layers comprising abarrier coat having a continuous fused polymer phase with talc particlesembedded therein, wherein the talc particles constitute 30-75% of thetotal weight of the coat, said barrier coat lying on the inside of thecontainer in contact with the food and constituting a barrier to liquidand gas transmission; and wherein the fiber board base has a middlelayer of a blend of sulfate pulp and chemithermomechanical pulp andlayers of sulfate pulp on both sides of the middle layer.
 2. A frozenfood container made of a coated board, the board consisting of a fiberboard base of a weight from 130-500 g/m² and one or more superimposedpolymer-based coat layers, said layers comprising a barrier coat havinga continuous fused polymer phase with talc particles embedded therein,wherein the talc particles constitute 30-75% of the total weight of thecoat, said barrier coat lying on the inside of the container in contactwith the food and constituting a barrier to liquid and gas transmission;wherein the board comprises a three-layer fiber board base under saidbarrier coat; and wherein the three-layer fiber board base has a middlelayer of a blend of sulfate pulp and chemithermomechanical pulp andlayers of sulfate pulp on both sides of the middle layer.
 3. A frozenfood container according to claim 1 wherein the coated board has beenmade by a process comprising applying a polymer dispersion containingtalc particles onto a fiber board base as on-line coating in a boardmachine, the dispersed polymer particles being joined to one another toform in the finished dried coat a continuous polymer phase between talcparticles embedded therein, said polymer phase consisting of the polymerof said dispersed polymer particles and being formed without use of across-linking agent, and talc being used in an amount to form 30-75% ofthe total weight of the dried coat.
 4. A frozen food package, which is aclosed package comprising a container shaped as a tray with an edge rimand forming a substrate for ready-made food contained in the package,said tray being made of a board of superimposed material layersconsisting of a fiber board base of a weight from 130 to 500 g/m² and atleast one polymer-based coat applied onto the board base in a boardmachine and having a continuous fused polymer phase with talc particlesembedded therein, wherein the talc particles constitute 30-75% of thetotal weight of the coat, said coat forming the inside of the tray incontact with the packaged food and constituting an oxygen and aromabarrier and a barrier to liquid transmission; wherein the boardcomprises a three-layer fiber board base under said barrier coat, andwherein the three-layer fiber board base has a middle layer of a blendof sulfate pulp and chemithermomechanical pulp and layers of sulfatepulp on both sides of the middle layer.
 5. A food package comprising acontainer shaped as a tray with an edge rim, said tray being made of aboard of superimposed material layers consisting of a fiber board baseof a weight from 130 to 500 g/m² and at least one polymer-based coathaving a continuous fused polymer phase with talc particles embeddedtherein, wherein the talc particles constitute 30-75% of the totalweight of the coat, said coat forming the inside of the tray in contactwith the packaged food and constituting a barrier to liquid and gastransmission; wherein the board comprises a three-layer fiber board baseunder said barrier coat, and wherein the three-layer fiber board basehas a middle layer of a blend of sulfate pulp and chemithermomechanicalpulp and layers of sulfate pulp on both sides of the middle layer.
 6. Adisposable drinking mug made of coated board comprising a fiber boardbase of a weight 130-500 g/m², and at least one polymer-based coat onthe board base, the coat comprising a continuous fused polymer phasewith talc particles embedded therein, wherein the talc particlesconstitute 30-75% of the total weight of the coat; wherein the boardcomprises a three-layer fiber board base under said barrier coat, andwherein the three-layer fiber board base has a middle layer of a blendof sulfate pulp and chemithermomechanical pulp and layers of sulfatepulp on both sides of the middle layer.
 7. A disposable drinking mugmade of coated board comprising a fiber board base of a weight from130-500 g/m², and at least one polymer-based coat on the board base, thecoat comprising a continuous fused polymer phase with talc particlesembedded therein, wherein the talc particles constitute 30-75% of thetotal weight of the coat; wherein the three-layer fiber board has amiddle layer of a blend of sulfate pulp and chemithermomechanical pulpand layers of sulfate pulp on both sides of the middle layer.